Use typing to reduce chances of IPv4 endianness errors

We recently corrected some errors handling the endianness of IPv4
addresses.  These are very easy errors to make since although we mostly
store them in network endianness, we sometimes need to manipulate them in
host endianness.

To reduce the chances of making such mistakes again, change to always using
a (struct in_addr) instead of a bare in_addr_t or uint32_t to store network
endian addresses.  This makes it harder to accidentally do arithmetic or
comparisons on such addresses as if they were host endian.

We introduce a number of IN4_IS_ADDR_*() helpers to make it easier to
directly work with struct in_addr values.  This has the additional benefit
of making the IPv4 and IPv6 paths more visually similar.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 15 insertions, 15 deletions

diff --git a/udp.c b/udp.c
index 7ce533d..fca418d 100644
--- a/udp.c
+++ b/udp.c
@@ -298,7 +298,7 @@ static void udp_update_check4(struct udp4_l2_buf_t *buf)
  * @ip_da:	Pointer to IPv4 destination address, NULL if unchanged
  */
 void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
-		       const uint32_t *ip_da)
+		       const struct in_addr *ip_da)
 {
 	int i;
 
@@ -317,7 +317,7 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
 		}
 
 		if (ip_da) {
-			b4->iph.daddr = *ip_da;
+			b4->iph.daddr = ip_da->s_addr;
 			if (!i) {
 				b4->iph.saddr = 0;
 				b4->iph.tot_len = 0;
@@ -671,30 +671,30 @@ static void udp_sock_fill_data_v4(const struct ctx *c, int n,
 	struct udp4_l2_buf_t *b = &udp4_l2_buf[n];
 	size_t ip_len, buf_len;
 	in_port_t src_port;
-	in_addr_t src;
 
 	ip_len = udp4_l2_mh_sock[n].msg_len + sizeof(b->iph) + sizeof(b->uh);
 
 	b->iph.tot_len = htons(ip_len);
 
-	src = ntohl(b->s_in.sin_addr.s_addr);
 	src_port = ntohs(b->s_in.sin_port);
 
-	if (IPV4_IS_LOOPBACK(src) ||
-	    src == INADDR_ANY || src == ntohl(c->ip4.addr_seen)) {
-		b->iph.saddr = c->ip4.gw;
+	if (IN4_IS_ADDR_LOOPBACK(&b->s_in.sin_addr) ||
+	    IN4_IS_ADDR_UNSPECIFIED(&b->s_in.sin_addr)||
+	    IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.addr_seen)) {
+		b->iph.saddr = c->ip4.gw.s_addr;
 		udp_tap_map[V4][src_port].ts = now->tv_sec;
 		udp_tap_map[V4][src_port].flags |= PORT_LOCAL;
 
-		if (b->s_in.sin_addr.s_addr == c->ip4.addr_seen)
+		if (IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr.s_addr, &c->ip4.addr_seen))
 			udp_tap_map[V4][src_port].flags &= ~PORT_LOOPBACK;
 		else
 			udp_tap_map[V4][src_port].flags |= PORT_LOOPBACK;
 
 		bitmap_set(udp_act[V4][UDP_ACT_TAP], src_port);
-	} else if (c->ip4.dns_fwd &&
-		   src == htonl(c->ip4.dns[0]) && src_port == 53) {
-		b->iph.saddr = c->ip4.dns_fwd;
+	} else if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_fwd) &&
+		   IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.dns[0]) &&
+		   src_port == 53) {
+		b->iph.saddr = c->ip4.dns_fwd.s_addr;
 	} else {
 		b->iph.saddr = b->s_in.sin_addr.s_addr;
 	}
@@ -1016,15 +1016,15 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 
 		udp_tap_map[V4][src].ts = now->tv_sec;
 
-		if (s_in.sin_addr.s_addr == c->ip4.gw && !c->no_map_gw) {
+		if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.gw) && !c->no_map_gw) {
 			if (!(udp_tap_map[V4][dst].flags & PORT_LOCAL) ||
 			    (udp_tap_map[V4][dst].flags & PORT_LOOPBACK))
 				s_in.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 			else
-				s_in.sin_addr.s_addr = c->ip4.addr_seen;
-		} else if (s_in.sin_addr.s_addr == c->ip4.dns_fwd &&
+				s_in.sin_addr = c->ip4.addr_seen;
+		} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.dns_fwd) &&
 			   ntohs(s_in.sin_port) == 53) {
-			s_in.sin_addr.s_addr = c->ip4.dns[0];
+			s_in.sin_addr = c->ip4.dns[0];
 		}
 	} else {
 		s_in6 = (struct sockaddr_in6) {